The use of RF energy in the medical field is known. For example U.S. Pat. No. 4,716,897 to Noguchi et al. discloses an electrosurgical apparatus that includes a radio frequency (RF) power source for supplying an object to be cauterized through a treatment tool and an electrode plate.
In addition, hyperthermia has been applied with increasing success for therapy of malignant tumors, both as an adjuvant to ionizing radiation and chemotherapy and also as a singular modality in which tissue temperatures are elevated sufficiently to produce cellular death. In both cases, it is desireable to induce a state of hyperthermia that is localized by interstitial current heating to a specific area while concurrently insuring minimum thermal damage to healthy surrounding tissue. Often, the tumor is located subcutaneously and its healing requires either surgery, endoscopy procedures or external radiation. However, externally inducing a state of hyperthermia in deep body tissue is difficult to accomplish because the current density is diluted due to its absorption by healthy tissue. In addition, a portion of the RF energy is reflected at the muscle/fat and bone interfaces which adds to the problem of depositing a known quantity of energy directly on a small tumor. Similarly, it is known to use microwave antenna catheters inserted through endoscopes to irradiate tumors. However, this method is not without its drawbacks since the microwave catheter acts as an antenna wherein the energy radiates in all directions and the amount of energy reaching the tumor is difficult to determine with precision. The measurement of the amount of energy reaching the tumor becomes important because the rate of tissue damage increases as an exponential function of absolute temperature and the cummulative injury accrues linearly with time. In addition, the period of time that the surgeon can remain within the body is limited and microwave deposition of energy requires the antenna to be present within the body for an extended period of time.
It is, therefore, an object of the present invention to provide an effective treatment for deep tumors using an endoscope.
It is another object of the present invention to provide an effective treatment for deep tumors that uses RF energy to deposit a known quantity of energy on the tumor.
It is still another object of the present invention to provide an effective treatment for deep tumors that minimizes the damage to the surrounding healthy tissue.
It is a further object of the invention to provide an effective treatment for deep tumors that minimizes the invasiveness of the therapy.
It is yet another object of the present invention to treat the tumor using RF energy to quickly elevate the temperature of the tumor to a predetermined level.